STEAP4 and HIF-1α gene expressions in visceral and subcutaneous adipose tissue of the morbidly obese patients

Aim and background: Obesity is a multifactorial disease in which environmental and genetic factors play an integrated role. Determining such target genes will help to elucidate the mechanisms underlying complex diseases such as obesity and diabetes which are usually seen together. Present study investigates the expression levels of STEAP4 and HIF-1α in visceral and subcutaneous adipose tissue. Patients and methods: 30(6 M) morbidly obese patients undergoing bariatric surgery were included in the study. The patients were grouped according to the BMI as Group I (BMI <50 kg/m²) and Group II (BMI ≥50 kg/m²). Samples from visceral (omentum) and subcutaneous adipose tissues were obtained from each patient and real-time PCR (qPCR) was carried out for STEAP4 and HIF-1α gene expressions. Correlations between expression levels and clinical parameters were analyzed. Results: Mean age of the patients recruited to the study was 37.4 (18-64) years. Mean BMI was 46 (36-60) kg/m². STEAP4 expression in visceral adipose tissue was significantly higher than subcutaneous tissue. Visceral STEAP4 expression was also found to be reduced with increased BMI. It was also lower in patients with HbA₁C over 6. Furthermore, expression of subcutaneous and visceral HIF-1α was significantly higher in Group II. There was a significant correlation between BMI, glycosylated hemoglobin, STEAP4 and HIF-1α gene expression. Conclusions: Obesity and related disease are linked with the fact that there is a low grade inflammation in the adipose tissue of the obese individuals. Counter-regulatory processes such as STEAP4 protein family are overwhelmed by the proinflammatory stimuli. HIF-1α expression is increased due to tissue hypoxia and pro-inflammatory stimuli in the obese individuals, which results in increased visceral STEAP4 expressions.